Mechanism and method for classifying and assorting metal sheets



B. CAMP 2,950,640 on FOR CLASSIFYING AND a METAL SHEETS J. MECHANISM ANDMETH ASSORTIN Aug. 30, 1960 6 Sheets-Sheet 1 Filed Nov. 28, 1951 J. B.CAMP 2,950,640 MECHANISM MET FOR CLASSIFYING AND SORTI METAL SHEETS HODNG Aug. 30, 1960 6 Sheets-Sheet 2 Filed Nov. 28, 1951 FIE-l4- Ioweniar:J4ME 5. (4M2 Aug. 30, 1960 J. B. CAMP MECHANISM AND METHOD FORCLASSIF'YING AND ASSORTING METAL SHEETS 6 Sheets-Sheet 3 Filed Nov. 28,1951 Aug, 30, 1-960 J. B. CAMP 2,950,640

MECHANISM AND METHOD FOR CLASSIFYING AND ASSORTING METAL SHEETS FiledNov. 28, 1951 6 Sheets-Sheet 4 Aug, 30, 1960 J. B. CAMP MECHANISM ANDMETHOD FOR CLASSIFYING AND ASSORTING METAL SHEETS 6 Sheets-Sheet 5 FiledNov. 28, 1951 J. B. CAMP MECHANISM AND METHOD FOR CLASSIFYING AND Aug.3@, 1960 ASSORTING METAL SHEETS 6 Sheets-Sheet 6 Filed Nov. 28, 1951 Eum & wm p w m v n 6 6 lhl PQQ. M M N C V q m A @L w, HF J u n L J QM g.m 3% fi a n w n fl EN 3L0 m n i Q mm QWN .v $5M. T r 5: L n w n wal WWWm @ww. IL mw m a \wm (13 lllll I]: WQRRPQ mmfigxgm QQW R\ 55% wmthmkv uMECHANISM AND lVIETHOD FOR CLASSIFYING AND ASSORTING lVIETAL SHEETSJames B. Camp, Fair-field, Ala, assignor to United States SteelCorporation, a corporation of New Jersey Filed Nov. 28, 1951, Ser. No.258,700

20 Claims. (CI. 83-29) This invention relates to an improved mechanismand method for classifying and assorting metal sheets in high speedshear lines.

Modern practice in shearing metal strip into sheets is to feed the stripfrom an uncoiler through a roller leveler and a rotary flying shear,which cuts the strip to sheets of appropriate length, and to a conveyorwhich carries the sheets to pilers. Such shear lines are equipped withmechanism which automatically classifies and assorts the sheets. Thismechanism comprises essentially a means for detecting imperfections inthe strip ahead of the shear, a deflector at the exit end of theconveyor, and a time delay means for operating the deflector at theproper interval after an imperfection has been detected. Normally thedeflector allows prime sheets to pass to a prime sheet piler, but, whenoperated by the detecting and time delay means, it diverts imperfectsheets to a reject sheet piler. The detecting means commonly includes alight sensitive device for detecting pin holes and a gauge for detectingoff-gauge thickness. Usually there is a marking device which embossesthe strip opposite the pin holes to aid in subsequent identification ofdefective sheets. Such shear lines are used, for example, for shearingand assorting electrolytically tinned steel strip or black plate steelstrip preliminary to hot dip tinning.

Previous classifying and assorting mechanisms with which I am familiarrelay largely on mechanical devices, commonly embodying pin wheeltimers, several relays and switches, and mechanical deflectors. Theyrespond rather slowly and also require frequent maintenance andadjustment. In high speed lines, each time the deflector operates, itdiverts to the reject piler at least three sheets and often more.Consequently several prime sheets go to the reject pile whenever thedeflector operates to divert one or more imperfect sheets, and thesheets in the reject pile subsequently must be hand-inspected to salvageprimes. Cobbles in the line are frequent due to operation of themechanical deflector while a sheet is passing it. Timing of the markeris not sufliciently precise to insure always marking the right sheet,particularly for imperfections near a shear cut. The deflector mustoperate ahead of the leading edge of the imperfect sheet, yet thereference point from which timing begins is either the defect itself orelse the cutting of the trailing edge of a defective sheet by the shear,an arrangement which can induce a further inaccuracy.

An object of the present invention is to provide an improved classifyingand assorting mechanism which responds quickly enough to divert singlesheets from a high speed shear line and thus diverts only sheetsactually having imperfections unaccompanied by prime sheets.

A further object of the invention is to provide an improved classifyingand asserting mechanism which largely eliminates mechanically movingparts, but instead embodies a magnetic memory device, a magnetic rolldeflector, and an electronic circuit for recording imperfecnited StatesPatent tions in the memory device and subsequently operating thedeflector therefiom.

A further object of the invention is to provide an improved classifyingand asserting mechanism and method which transfer the reference pointfor timing deflector operation to the leading edge of each imperfectsheet.

A further object of the invention is to provide an improved classifyingand assorting mechanism Which times operation of the marker veryprecisely from the same memory device that times operation of thedeflector and thereby insures that the mark is applied opposite theimperfection.

A further object of the invention is to provide an improved classifyingand assorting mechanism and method which insure with complete certaintythat every sheet containing an imperfection and only those sheets arediverted to the reject pile.

In accomplishing these and other objects of the invention, I haveprovide improved details of structure, a preferred form of which isshown in the accompanying drawings, in which:

Figure 1 is a schematic side elevational view of a shear line which isequipped with a classifying and assorting mechanism embodying featuresof the present invention;

Figure 2 is a vertical sectional view of the magnetic roll embodied inthe preferred deflector;

Figure 3 is a sectional view taken substantially on line I1l-III ofFigure 2;

Figure 4 is a vertical sectional view of the preferred memory device;

Figures 5 and 6 are vertical sectional views on a larger scaleofrecording heads or pickups embodied in the memory device; and

Figures 7, 7a, 7b and together are a wiring diagram of the electroniccontrol.

Figure 1 shows schematically a shear line which comprises a rollerleveler 1, a rotary flying shear 2, a conveyor 3, a prime sheet piler 4and a reject sheet piler 5. These parts can be of any standard ordesired construction and therefore are not shown in detail. Strip Senters from the left from an uncoiler, not shown, and passes through theroller leveler and the shear. The latter cuts it into sheets :8 whichare deposited on the conveyor and travel to the pilers. A deflector isinterposed between the exit end of the conveyor and the pilers. Normallythis deflector allows prime sheets to pass undisturbed to the primepiler, but it can be operated by the detecting means and time delaymeans hereinafter described to divert imperfect sheets to the rejectpiler.

The preferred deflector comprises a fixed blade 7 and a normallymagnetized roll 8 driven at about the same circumferential speed as thelinear speed of the conveyor 3. The blade is spaced from the exit end ofthe conveyor and directed theretoward. The roll is situated above thespace between the conveyor 3 and the blade 7. As long as the roll ismagnetized, it carries sheets discharging from the conveyor across theblade to the prime piler 4. When demagnetized, the roll allows sheetsfrom the conveyor to pass underneath the blade to the reject piler 5.

Figures 2 and 3 show details of roll 8 and its mounting. The rollincludes a body, a fixed shaft 9 on which the body is rotatably mountedon antifriction bearings 10, and a drive pulley 11 fixed to one end ofthe body. Shaft 9 is supported on brackets 12 fixed to the conveyorframe. The roll body is hollow and of a nonmagnetic metal, such asbrass, stainless steel, or the nickel alloy sold under the trademarkInconel. Within the body the shaft carries electromagnets .13 which havedownwardly directed poles. The roll is in effect magnetized whenever themagnets are energized and attracts sheets to its outer surface. 7

A deflector thus constructed is especially quick acting. Theelectromagnets 13 can be' deenergized and the roll demagnetized duringthe very brief interval after the trailing edge of a rapidly movingsheet has passed the roll and before the leading edge of the next sheetarrives. The electromagnets can be energized again and the rollmagnetized during the next such interval. This quick action enables thedeflector to divert only a single imperfect sheetto the reject piler, oras many in succession as are imperfect, without diverting any primes.Nevertheless the remainder of the classifying and assorting mechanismcould be used with other deflectors, even though they might not actquickly enough to accomplish the object of diverting only imperfectsheets unaccompanied by primes. a

Thedetecting means includes a light sensitive pin hole detector 14 and athickness gauge 15 both situated ahead of the roller leveler. Betweenthe detector and gauge there is preferably a marker 16 for marking themargin of the strip opposite each pin hole to facilitate identification.The pin hole detector, marker and thickness gauge can be any standard ordesired commercial devices suitable'for this purpose and therefore arenot shown 1101 described in detail. Nevertheless, as a detector I.prefer to employ a General Electric Super Sensitive Pin Hole Detector,since it furnishes a fine straight line of high intensity light thatcan'detect extremely fine pin holes. The detecting means is connected tothe deflector through time delay means which comprises essentially anelectronic control, the circuits of which are shown only in block inFigure 1 but are hereinafter fully described, and a memory device. a

As shown in Figures '4, and 6, the memory device includes a nonmagneticrotor 19, which preferably is a machined aluminum casting and carriesaround its circumference two recording tracks 20 and 21 formed of alarge number of turns of magnetic recording wire. The rotor is chaindriven from the roller leveler 1 so that both recording tracks travel ata-rate directly proportional to the rate of striptravelr Track 20 has apinhole recording'head 22, and off-gauge recording head 23, a markerpickup 24, a circuit cocking pickup'25 and a permanent magnet eraser 26(Figure 1). Track 21 has a recording head 27, a pickup 28 and apermanent magnet eraser 29. These recording heads contain magnetizingcoils which, when energized, magnet-ize'the adjacent portion of therecording track 20 or 21. Subsequent rotationofthe recording trackcarries the'magnetized spot opposite one of the pickups, in which itinduces an electric current. Any magnetized spots are removed as theypass the eraser 26 or 29. The memory device is shown somewhatschematically in the present application, but is shown in detail andclaimed in my joint application with ColemanH. wats'on, Serial No.258,699, filed November 28, l951,-now Patent No. 2,735,987, entitledMagnetic Memory Device.

The pin hole detector 14 is connected to the pin hole recording head-22via a pulse shaping circuit 30 and an amplifier circuit31 of theelectronic control. Simi larly the thickness gauge is connected to theoff-gauge recording head 23 via an amplifier circuit 32. Whenever thepin hole detector ,or the thickness gaugedetects an imperfection in thestrip, it energizes the magnetizing coil of the corresponding recordinghead 22 or 23 through the electronic control and thus magnetizes a spoton the recording track 20. g The spacing between the recording head 22and the marker pickup 24 is proportional to that between the pin holedetector 14 and the marker 16. The marker pickup .is connected to themarker via an amplifier circuit 33 of the electronic control; 'Wheneverthe pin hole recording head 22 (but not head 23) magnetizes aspot on therecording track 20, this spot subsequently energizes the marker pickup24 and actuates the marker 16 as the pin hole passes the marker. Thespacing between the recording head 22 and the circuit cocking pickup 25is proportional to that between the pin hole detector and the rotaryelements of the shear 2. Like, wise the spacing between the recordinghead 23 and the pickup 25 is proportional .tothat between the thicknessgauge and the rotary elements of the shear. Consequently any spotmagnetized on the recording track by either recording head 22 or 23reaches the pickup simultaneously with the arrival of the imperfectionin the strip at the shear. The pickup 25 is connected to a first storagecircuit 34 in the electronic control via an amplifier circuit 35.Energization of the pickup 25 cocks this storage circuit, so that now itis recorded in the control that the next sheet cut from the strip willcontain an imperfection and should go to the reject piler.

A normally closed shear switch 36 is connected to the storage circuit 34via an amplifier circuit 37. Once each revolution of the shear 2, as theshear cuts, this switch momentarily opens. If the storage circuit iscocked, opening of switch 36 triggers it; otherwise its opening has noeffect. Triggering the storage circuit resets this circuit, cocks asecond storage circuit 38 in the electronic control, and thus recordsthat the sheet last cut contains an imperfection.

At this stage the reference point is of course the trailing edge of thesheet last cut. For greater accuracy the mechanism of the presentinvention transfers this reference point to the leading edge. Thetransferring means includes a photoelectric cell 39 below conveyor 3 andbeyond shear 2 and a light source 40 above the conveyor in line withsaid cell. The spacing between the cell and the shear must exceed onesheet length, but must not be suflicient for two full sheets to betherebetween; that is, after the shear cuts a sheet from the strip, thenext leading edge which passes the cell must be the leading edge of thatsheet. The cell 39 is connected to a flipflop circuit 41, which in turnis connected to the second storage circuit 38 and to a third storagecircuit 42 all in the electronic control. As fully explainedhereinafter, the flip-flop 41 has two alternative current paths, one ofwhich conducts current when cell 39 is exposed to the flight source 40,but not when it is darkened by a sheet between the cell and the lightsource, and the other of which does the reverse. With circuit 38 cocked,when the leading edge of a sheet passes between the light source and thecell and circuit 41 thus flips, the latter triggers circuit 38. Eachsuch triggering changes the current path through a third storage circuit42.

The storage circuit 42 is connected to an oscillator circuit 43, whichin turn is connected to the recording 7 head 27 of the second recordingtrack 21 of the memory device. I Whenever the storage circuit 38 istriggered (i.e., if circuit 38 was cocked when the leading edge of asheet darkened the photoelectric cell 39), the circuit 42 keys theoscillator 43, which thereupon sends current to the recording head 27.The storage circuit 38 immediately resets, but the storage circuit 42continues to key the oscillator as long as the photoelectric cell 39 isdarkened -(i.e., until the trailing edge of the imperfect sheet passesthis cell). Consequently the recording head 27 remains energized untilthe trailing edge of the imperfect sheet passes the photoelectric celland again exposes this cell to the light source 40. Thus the recordinghead 27 magnetizes an arc of the recording track 21 proportional to thelength of the imperfect sheet. Since circuit 38 resets immediately, itcan be cocked again by detection of a second imperfect sheet anywherefollowing the first. even next to it.

The spacing between the recording head 27 and the pickup 28 isproportional to that between the photoelectriccell 39 and thedeflectorroll 8. The electromagnets 13 of the latter normally. are energized viaa grid controlled rectifier 44. The pickup/28 E connected to the gridsof the rectifier 44 via an amplifier 45. When a magnetized lents arepossible.

part of the track 21 energizes the pickup 28, the rectifier 44- ceasesto pass current to the electromagnets. Consequently they aredeenergized, and the sheet is diverted to the reject piler 5. The timingof course is accurately adjusted so that the electromagnets aredeenergized an instant before the arrival of the imperfect sheet andagain energized an instant after it clears roll 8.

Electronic control Figures 7, 7a, 7b and 7c together show a Wiringdiagram of an exemplary arrangement of circuits in the electroniccontrol, but it is obvious that many equiva- To facilitate describingthese circuits the ensuing description indicates possible actualnumerical values of some of the voltages and resistances, but it is tobe understood these values are only exemplary and could be varied widelyWithout departing from the invention.

Referring first to Figure 7, the circuit includes a grounded line 50 ofzero potential, a line 51 of relatively high positive D.C. potential,and a line 52 of relatively high negative D.C. potential energized byany suitable outside power source not shown. For example, the line 51can be at 265 volts positive and the line 52 at 300 volts negative. Aconductor 53 extends between lines 51 and 50 and contains fiveresistances 54 to 58, which can be for example of 10,000 ohms, 5,000ohms, 5,000 ohms, 300 ohms and 150 ohms respectively. Four conductors 59to 62 are connected to conductor 53 between the various resistances andthus have successively diminishing positive potentials, which can be forexample 132 volts, 68 volts, 6 volts and 2 volts respectively. Similarlya conductor 63 extends between lines 52 and 50 and contains fourresistances 64- to 67, which can be for example of 15,000 ohms, 12,500ohms, 1500 ohms and 1500 ohms respectively. Three conductors 68, 69 and'70 are connected to conductor 63 between the various resistances andthus have successively diminishing negative potentials, which can be forexample 108 volts, 20 volts and volts respectively.

The pulse shaping circuit 30 of the control includes a dual Triodevacuum tube 71 (for example that designated in the trade as 6SN7) whichreceives impulses of any shape from the pin hole detector 1 andtransmits a sharply peaked pulse, always of the same magnitude andshape, to be recorded on the track of the memory device. A conductor 72containing a 220,000 ohm resistance 73 connects the left plate of thistube to line 51 (potential 265 volts positive) and a conductor 74containing a 22,000 ohms resistance 75 connects the right plate also toline 51. A conductor 76 containing a resistance 77 connects bothcathodes of this tube to the grounded line 50. A conductor 78,containing a condenser 79 and a 500,000 ohm resistance 80 in parallel,connects the right grid of this tube with line 51 via the conductor 72and resistance 73. A conductor 81 con taining a one megohm resistance 82connects the right grid to the line 52 (potential 300 volts negative)via the conductor 78. A conductor 83 containing a condenser 84 and a100,000 ohm resistance 85 in series connects the pin hole detector 14with conductor 70 (potential 10 volts negative). A conductor 510,000 ohmresistance 87 connects an intermediate point on resistance 85 with theleft grid of the tube. Normally the right grid of tube 71 is positivewith respect to the cathode, since it receives a positive potential of15 /2 volts from line 51 via conductors 72 and 78, which potentialovercomes the smaller negative potential from line 52 received throughthe megohm resistance 82. Normally the left grid of tube 71 is negativewith respect to the cathode, since it reecives a negative potential fromconductor 70 (potential 10 volts negative) via conductors 83 and 86.Consequently current normally flows through the right side of this tube,but not through the left side.

Since resistance 75 is relatively small, this current is relav 86containing a.

tively large and produces a relatively large voltage drop acrossresistance 77.

When a pin hole in the strip passes the pin hole detector 14, the lattertransmits both a positive and a negative pulse through the condenser 84,the magntiude and shape of which vary with the size of pin hole. Thenegative pulse has no effect, but the positive pulse momentarilyovercomes the negative charge on the left grid of tube 71 and thusmomentarily allows current to flow through the left side of the tube.Since resistance 73 is much higher than resistance 75, the currentthrough the left side is is much smaller than the normal current throughthe right side, but it causes a voltage drop across resistance 73 andovercomes the positive charge on the right grid, which thereuponreceives a negative charge from line 52 via conductor 81. The smallercurrent through the left side of tube 71 produces only a negligiblevoltage drop across resistance 77, whereby a stoppage of current throughthe right side of this tube can be regarded as eliminating the voltagedrop across this resistance. A critical point occurs when the left gridreaches a potential which switches conduction through the tube almostinstantaneously from the right to the left side. This critical point andresultant switch occur because elimination of the voltage drop acrossthe resistance 77 is equivalent to adding this voltage change to thepulse from detector 14 and in effect makes the left grid immediatelymore positive. A conductor 88 is connected between conductor 74- andconductor 69 and contains a condenser 39 and a resistance 90 in series.A sudden stoppage of current through the right side of the tube producesa sudden current surge through conductor 88 and condenser 89 and appliespositive voltage to the grids of a tube 91 of the amplifier circuit 31,next described.

The tube 91 of amplifier circuit 31 is another dual Triode (for examplethat designated in the trade as 6N7) and it energizes the magnetizingcoil of the pin hole recording head 22 in response to pulses inconductor 88. A conductor 92 connects both plates of this tube to oneend of the primary coil of a transformer 93, the other end of which isconnected to line 51. A conductor 95 connects both cathodes of tube 91to the grounded line 50. A conductor 96 containing a damping rectifier97 connects conductor 92 and line 51. Said rectifier prevents anoscillating potential from appearing from the plate of tube 91.Conductor 88 is connected to both grids of the tube via a resistance 99.

Normally both grids of tube 91 are negative with respect to thecathodes, since they receive a negative potential from conductor 69(potential 20 volts negative) via conductor 88. Consequently no currentflows through either side of this tube. A current surge throughconductor 88 produces both a positive and a negative pulse. The negativepulse has no effect, but the positive pulse momentarily applies apositive charge to both grids of tube 91. Now for an instant anamplified current flows through both sides of this tube and energizesthe primary coil of transformer 93. The current path is from thegrounded line 50 via conductor 95, the cathodes and plates of the tube,conductor 92, and the primary coil of the transformer 93, to line 51.Conductors 100 connect the ends of the secondary transformer coil to themagnetizing coil of the recording head 22. Thus a momentary current isinduced in the secondary coil of the transformer and it energizes themagnetizing coil and magnetizes a spot on the recording track 20.Energization of the magnetizing coil is only momentary, since the gridsof tube 91 quickly resume their negative charge after the current surgethrough conductor 88 dissipates.

The coil of the marker pickup 24 is grounded at one end and connected atthe other end via a conductor 101 to the primary coil of a transformer102 of the amplifier circuit 33. This primary coil is connected to thegrounded line 50 via a conductor 103. The amplifier circuit 33 includesa combined amplifier and rectifier tube 104 (for example that designatedin the trade as ,6AQ7 The left or" amplifier side of tube 104 has aplate con.- nected to line 51 (potential 265 voltspositive) via aconductor. 105 containing resistances 106 and 107 in series. The leftside of tube 104 also has a cathode which is connected to the groundedline 50 Via conductor 1113 and a conductor containing a condenser 109and a resistance 110 in. parallel. One end of the secondary coil oftransformer 102 is connected to a grid in the left side of tube 104 viaa conductor 111 and the other end. of the secondary cofl is connected tothe grounded line 50 via conductors 103 and 108. A resistance 112 isconnected across the secondary coil. A

conductor 113 containing a condenser 114 is connected between conductor105 intermediate its resistances 166 and 107 and grounded conductors103and 108.

When a magnetized spot in the recording track induces a current in themarker pickup 24 and hence in the primary coil of transformer 102', theresulting current surge in the secondary coil of the transformer appliesfirst a positive and then a negative charge to the left grid of tube104. The positive charge causes an amplified current'surge to flowthrough the left side of the tube. The current path is from groundedline 50 via conductors 103 and 108, the parallel condenser 109 andresistance 110, the left. cathode and plate of tube 104, and conductor105 to line 51 (potential 265 volts P051: tive).

A conductor 115 containing a resistance 116 and a condenser 1 7 inseries is connected between conductors 105 and 61 (potential 6 voltspositive). The right or rectifier side of tube 104 has a cathodeconnected to conductor 115 and a pair of plates connected to a conductor118. The amplifier circuit 33 also includes a dual Triode tube 119,which can be of the same type .as tube 71 (6SN7).. A conductor 120containing a resistance 121 connects the left plate with line 51(potential 265 volts positive). A conductor 122 containing a markerrelay coil 123 connects the right plate also with line 51. A conductor124 connects both cathodes of tube 119 with the grounded line 50. Theaforementioned conductor 118 is connected between conductor 68(potential 108 volts negative) and conductor 122' and contains a 330,000ohm resistance 125. and a 500,000 ohm resistance 126 in seriesonopposite sides of its cormection to the right plates of tube 104.Conductor 118 also is connected to the left grid of tube 119. Aconductor 127 containing a condenser .128, a 2 megohm variableresistance 129 and a 100,000 ohm resistance 130. all in series isconnected to conductor 120 and to a conductor 131. The latter isconnected to conductor 68 (potential 108 volts negative) via a 50,000ohm resistance 132 and to the grounded line 50 via another 50,000 ohmresistance 133 and in the present example has a potential of 54 voltsnegative. Conductor 127 is connected to the right grid of tube 119 via aresistance 13 4. Normally the positive and negative chargeson the leftgrid of tube 119 balance each otherso that the grid is at zeropotential. Normally the right grid has a 52 volt negative chargereceived via conductor 131 (potential 54 volts negative) and conductor1127. Consequently current normally flows .throughthe left sideof thetube but not 7 through the right sicle.

The'amplified positive and negative pulses from the left side oftube'104 send a negative and a positive pulse through conductor 115 viaits condenser 117. The rectifierside of tube 104 passes the negativepulse, which thus applies a negative charge to the left grid of tube119. The resistance 116 dissipates the positive pulse. The negativepulse thusmomentarily stops the flow of current through the left side oftube 119. This current stoppageproduces both a positive. and a negativepulse through conductor 127 because ofthe actionof condenser 12S.The'positive pulse'prcduces a momentary; positive charge on the rightgrid of tube 119 and a current flow through the right side of the tube.The current path is from the grounded line 50 via conductor 124, theright cathode and plate, conductor 1 2 2, and relay coil. 123 to line51. A diode tube 135 is connected to conductor 127 to dissipate thepositive pulse from condenser 128.

Energization of coil 123 operates the marker 16 to mark the stripopposite the pin hole. The relay 123 preferably is the only mechanicalrelay in the entire circuit Its operation is accurately timed withmovement of the strip, since it is controlled by the recording track 20of the memory device driven at a speeed proportionalto the strip speed.a

. The amplifier circuit 32, through which the thickness gauge 15energizes the magnetizing coil of its recording head 23 in response toelf-gauge thickness in the strip, includes essentially a transformer 136and an oscillator tube 137 (for example that known in the trade as 6F6).The primary coil of transformer 136v is connected to an AC. line 138 andto the plate and one grid of tube 137 via a conductor 139. A conductor140 connects the cathode of tube 137 with the grounded line 50. Aconductor 141 containing a resistance 142 connects the other grid oftube137 with conductor 131 (potential 54 volts negative) and thus normallyapplies a negative charge which prevents current flow. The gaugelSincludes a normally open switch 143 which is in a conductor 144 thatconnects conductors 140 and 141. Whenever the strip is off-gauge, switch143 closes and thus grounds conductor 141 and removes the negativecharge from the grid. Thereupon current flows through tube 137 and theprimary coil of transformer 136. A resistance 145 and a condenser 146 inseries are connected across switch 143. The secondary coil oftransformer 136 is connected to the magnetizing. coil of the ofi-gaugerecording head 23 via conductors 147 and 148, so that current flowingthrough the primary coil induces a current in the secondary coil whichenergizes the magnetizing coil and Inagnetizes a spot on the recordingtrack 20.

When rotation of the recording track 20 moves a magnetized spot thereon(originating from either ,of the recording heads 22 or 23) alongsidepickup 25, the magnetized spot induces a current in the pickup and cocksthe first storage circuit 34 of the electronic control. Referring nextto Figure 7a; the coil of this pickup is grounded at one end andconnected at its other end via a conductor 149 to the primary coil of atransformer 150 of the amplifier circuit 35. A conductor 151connects theother end of this primary coil to the grounded line 50. The secondarycoil of transformer 150 is connected to an amplifier tube 152 (such asthat known in the trade as a 65]7) of the amplifier circuit 35. Thislatter circuit is well known and operates in the conventional Way;consequently it is not explained in detail, although Figure 7a containsa complete showing. The amplifier tube 152 transmits an amplifiedpositive. and negative pulse through a conductor 153 which contains acondenser 154 and a resistance 155 in series and is connected toconductor 70 (potential 10 volts negative).

The amplifier circuit 35 next includes a combined amplifier andrectifier tube 156 of the same type as tube 104 of the amplifyingcircuit 33 already described. Normally its grid at the left has anegative charge, but whenever a positive pulse passes throughcond-uctor153, the grid momentarily becomes positively charged. Tube 156 thereuponacts in the same fashion as already explained for tube 1134 andtransmits a, negative pulse through a conductor 157, which is connectedto its right plates and to conductor 63 (potential 108 volts negative).The operation of the tube and its circuit is not repeated in detail,since it is the same as for tube 104, although Figure 7a contains acomplete showing. M

The first st rage circuit 34 includes a dual Triode. tube 170,preferably similar to tubes 71 and 119. A conductor 171 containing a39,000 ohm resistance 172 connects the left plate to line 51 (potential265 volts positive). A conductor 173 containing a 39,000 ohm resistanceii-l connects the right plate also to line 51. A conductor 175 connectsboth cathodes to the grounded line 50. A conductor 179 containing acondenser 180 and a resistance 181 in series (Figure 7b) connectsconductor 171 with conductor 61 (potential 6 volts positive). Aconductor 132 containing a 200,000 ohm resistance 183 and a condenser184 in parallel connects the left grid with conductor 173. A conductor185 containing a 220,000 ohm resistance 3.86 connects the right gridwith conductor 68 (potential 108 volts negative). A conductor 137containing a 200,000 ohm resistance 188 and a condenser 189 in parallelconnects the right grid with conductor 171. A conductor 190 connects theleft grid with conductor 157.

Normally the left grid of tube 170 is positive with respect to thecathode, since it receives a positive charge from line 51 via conductors173 and 182. Normally the right grid is negative since it receives anegative charge via conductors 68 and 1'35. Consequently current flowsthrough the left side of the tube, but not the right side. However, whena rectified negative pulse appears in conductor 157, as alreadyexplained, it reaches the left grid via conductor 19%, overcomes thepositive charge and charges this grid negative and thus stops flow ofcurrent through the left side of the tube. Now current flowing inconductor 171 can go only through conductors 187 and 135, which areconnected to the right grid. This current overcomes the negative chargeon this grid and charges it positive. Current now flows through theright side of tube 170. With flow of current through tube 17% thusreversed from normal, the storage circuit 34 is cocked. Since therecording track 20 is synchronized to energize its pickup 25 when animperfection is exactly between the rotary elements of the shear 2, thestorage circuit become cocked virtually at this same instant.

Conductor 62. (potential 2 volts positive) is connected to the primarycoil of a transformer 191 of the amplifier circuit 37. A conductor 192?.containing a resistance 193 connects the other end of this primary coilwith the grounded line -9. Tire normally closed shear switch 36,hereinbefore referred to, is connected in parallel with resistance 193.The secondary coil of transformer 191 is connected to conductor -30(potential 68 volts positive) and to the grid of a Triode amplifier tube104 of the amplifier circuit 37.

As long as the shear switch 36 remains closed, direct current flowsthrough the primary coil of transformer 191, but such current does notpulse the secondary coil. Once each revolution of the shear at theinstant it cuts the strip S, the shear switch momentarily opens. Openingthis switch instantly cuts off the current flowing through the primarycoil and thus produces a negative pulse in the secondary coil and thegrid of tube 194. This pulse causes the plate of said tube to becomemore positive and thereby produces a positive pulse which is transmittedto the left grid of tube 17% via a rectifier tube 1&5 of the amplifiercircuit 37 and conductor 193. The operation of this portion of thecircuit is not explained in detail, as it follows well known principles,but the circuit is fully shown in Figure 7a. If current is flowingnormally through the left side of tube 170 (storage circuit not cocked),the positive pulse applied to the left grid has no effect since the gridalready is positive. However, if the storage circuit has been cocked andcurrent is flowing through the right side of tube 170, the positivepulse triggers the circuit. With the circuit cocked, the left grid isnegative with respect to the cathode. The positive pulse overcomes thenegative charge, causing current once more to flow through the left sideof the tube. Resumption of this current takes current away fromconductors 187 and 185, and the right grid again becomes negativelycharged. This current also produces a current pulse through conductor179because of the action of condenser 180 (Figure 7b). Triggering of thefirst storage circuit resets it, since it returns to its normal state,where it can again be cocked by an impulse from the pickup 25.

Referring next to Figure 7b, triggering the first storage circuit 34cocks the second storage circuit 38. The latter includes a dual Triodetube 201 which is of the same type as tube and similarly connected.Therefore the connection and immediately associated parts are notdescribed in detail, although fully shown in Figure 7b. Like tube 170,the left grid of tube 201 normally is charged positively and the rightgrid negatively, so that current normally flows through the left sidebut not the right. The left grid is connected to conductor 179 through arectifier 202 which passes only negative pulses. Thus pulses transmittedthrough conductor 179 apply a negative charge to the left grid of tube201 and change the flow of current therethrough and cock the circuit 38in the same fashion as pulses applied to the left grid of tube 3170 cockthe circuit 34.

Assuming that an imperfection has been detected, at this stage the sheetcontaining the imperfection has just been cut from the strip and lies onconveyor 3 in the space between shear 2 and the photoelectric cell 39.The reference point of the imperfect sheet is of course its trailingedge, which has just been cut by the shear. Next the photoelectric cellacts to transfer this reference point to the leading edge of the sheet.

Referring back to Figure 7, the anode of the photoelectric cell 32 isconnected to source of positive voltage (i.e., conductor 59) via avoltage divider comprised of resistances 203 and 2.05. The cathode isconnected to a source of negative voltage, through a conductor 206 whichcontains a resistance 207 and leads to a voltage divider comprised ofresistances 208 and 210. The cell passes current when exposed to light(i.e., when no sheet is passing between it and the light source 4-0),but not when darkened (i.e., when a sheet is passing). The potential ofconductor 206 is positive when current flows through the cell becausethe positive potential of conductor 59 (132 volts) overcomes the Weakernegative potential transmitted via resistances 207 and 208. Thepotential of conductor 2436 becomes negative when the cell is darkenedbecause the source of positive potential is cut off.

Referring again to Figure 7a, the flip-flop circuit 41 includes a dualTriode tube 211, which is connected similarly to the tube '71 andpreferably is the same type. Therefore no detailed description isincluded, although the connection is fully shown in Figure 7a. Aconductor 212 containing a resistance 213 conneots conductor 206 withthe left grid of tube 211. When conductor 206 has a positive potentialcaused by exposure of cell 39 to light, this grid bears a positivecharge and current flows through the left side of the tube, but not theright. When conductor 206 has a negative potential caused by darkeningof cell 39, this grid bears a negative charge and current flows throughthe right side, but not the left.

A conductor 214 containing a condenser 215 and a rectifier 216 isconnected between the current path through the right side of tube 211and the right grid of tube 201 (Figure 712). When current commences toflow through the right side of tube 211, the condenser and rectifiertransmit a negative pulse to the right grid of tube 201. If the secondstorage circuit 38 is in its normal uncooked state, the right gridalready is negative and the negative pulse has no effect. This pulsemerely marks the entry of the leading edge of a prime sheet opposite thecell 39. If this circuit is cocked, the negative pulse triggers it. Thispulse marks the entry of the leading edge of an imperfect sheet oppositethe cell. In the -cocked state the right grid of tube 201 is positiveand the negative pulse changes it back to negative and thus changes theflow of current through the tube conductor'223 containing a' condenser224.

back to the left side. A conductor 217 containing a condenser 218 and aresistance 219 in series is connected to the current path through theleft side of tube 201. When flow of current resumes through the leftside in response to triggering, the condenser causes a negative pulsethrough conductor 217. Conductor 217 is connected to a rectifier 220which leads to the third storage circuit 42 and transmits only thenegative pulse. Triggering of the storage circuit 38 also resets it.

Referring to Figure 7b, the third storage circuit 42 includes anotherdual Triode tube 221 of the same type and connected in the same fashionas tube 201, except that the rectifier 222 connected to its right grid(corresponds with rectifier 216) is connected also to the current paththrough the left side of tube 211 via a The left grid of tube 221 isconnected to the current path through the left side of tube 201 via therectifier 220. Normally the left grid of the tube 221 is positive andthe right grid negative so that current flows through the left side ofthe tube, but not through the right side. A negative pulse transmittedtothe left grid from conductor 217 and rectifier 224) reverses thiscurrent flow. In review such a negative pulse comes whenever the leadingedge of a previously identified imperfect sheet darkens thephotoelectric cell 39 and triggers the second storage circuit 38. w Aconductor 230 containing a 510,000 ohm resistance 231 and a,1.5 megohmresistance 232 is' connected to the current path through the left sideof tube 221 and to line 52 (potential 300 volts negative). An oscillatortube 233 of the oscillator 43 has its cathode connected to the groundedline 50 and its plate connected to line 51 (potential 265 voltspositive) via the primary coil of a transformer 234. A condenser 234a isconnected in parallel with this primary coil. The control grid isconnected to conductor 230 intermediate its resistance 231 and 232.Normally this grid bears a negative charge derived from line 52 and nocurrent flows through tube 233. When current ceases to flow through theleft side of tube 221, the additional positive potential is applied tothe grid of tube 233 via conductor 230 md resistance 231. This positivepotential overcomes the normal 'negative potential and keys theoscillator, which puts out an AC. voltage. A conductor 235 connects thesecondary coil of this transformer with the magnetizing coil of therecording head 27 on the recording track 21 of the memory device (Figure7c). The other end of this magnetizing coil is grounded.

As long as tube 233 puts out.an A.C. voltage, transformer 234 doeslikewise and the magnetizing coil is energized and magnetizes an arc oftherecording track 21. This coil remains energized as long as animperfec sheet is passing the photoelectric cell 39 and darkening thiscell. When the trailing edge of the imperfect sheet finally passes thecell and permits it again to conduct current, the left grid of tube 211of the flip-flop circuit 41 again assumes its positive charge, and theleft side of tube 211 commences to conduct current. A negative pulseappears'in conductor 223. The rectifier 222 transmits this pulse to theright grid of tube 221, which thereupon resumes its normal state inwhich its left side but not its right side conducts current. This actiontakes current from conductor 230 and the grid of oscillator 233 resumesits normal negative charge. Thus the magnetizing coil is deenergized.The length of arc magnetized on the recording track 21 is proportionalto the. length of the imperfect sheet, since the speed at which thistrack moves is proportional to the sheet speed and the time themagnetizing coil is energized equals the time required for the sheet topass a given point, i.e., the

V photoelectric cell 39.

' Referring to Figure 70, when rotation ofthe recording track 21 moves amagnetized portion thereon alongside the pickup 28 ('coincidentwith thearrival of the leading 12 edge of an imperfect sheet at the deflector),this portion of the track generates an AC. voltage in the pickup andcontinues to do so as long as it is passing. the pickup. The pickup coilis grounded at one end and connected at its other end via a conductor236 to the primary coil of a transformer 237. A conductor 238 connectsthe other .end of said primary coil to the grounded line 50. An

amplifier tube 239 of the amplifier circuit 45. is connected betweenline 51 and grounded line 50. The secondary coil of transformer 237 isconnected atone end to conductor 238 and thence to the grounded line 50and at its 250, so that the grid normally is negative with respect 7 to.the cathode, and the tube does not conduct current. A conductor 251containing a condenser 252'connects the grid of tube 245 to the currentpath through the amplifier tube 239.

A conductor 255 is connected between the plate of tube 245 and line 52and contains resistances 256 and 257 in series. The grid controlledrectifier 44 includes two Thyratron tubes 258 and 259, whose filamentsare connected to the grounded conductor 50 and to the secondary coil ofa transformer 260 in the fashion shown in Figure 7c. The primary coil ofthis transformer is connected to any suitable outside A.C. source forenergizing these filaments. A conductor 261 connects the grids of bothThyratron tubes with conductor 255, having resistances 262 and 263interposed therebetween. Normally both grids receive a positive chargederived from line 51, since the combined resistances 248 and 256 areconsiderably less than the resistance 257. A conductor 264 connects theplates of both Thyratron tubes with one side of the magnets 13 of themagnetic roll 8 through the center tap of a power transformer 265, whoseprimary coil is connected to any suitable A.C. source. The other side ofthese magnets is connected to the grounded line 50. Thus normally (i.e.,aslong as their grids are positive). the Thyratrons pass a rectifiedcurrent to the magnets 13 and keep the magnetic roll energized.

When a current is induced in the pick-up 28, this current acts throughthe amplifier tube 239 to overcome the negative charge on the grid oftube 245. The latter tube now conducts current and takes away thepositive potential of conductor 261. Thislatter conductor now receives anegative potential from line 52, which potential is applied to the gridsof both Thyratron tubes 258 and 259. These tubes cease to pass currentto the magnets 13, thus deenergizing the magnetic roll 8 and defleetingan imperfect sheet beneath blade 7. A resistance 266 and condenser 267preferably are connected across the magnets 13 to absorb the currentsurge produced by flux decay as the magnets are deenergized.

The magnets 13 remain deenergized until the magnetized Spot on track 21passes beyond the pickup 28. When no more current is induced in thispickup, thegrid of tube 245 resumes its negative charge, which in turnallows conductors 255 and 261 to resume their normal positive potential.Thus the grids of the Thyratronf tubes againybecome positive'and thetubes conduct current to the magnets 13 as before.

From the foregoing description it is seen that the magnetic roll 8 canbe deenergized .or energized almost instantancously. The reference pointwhich controls deenergization'is the leading edge of the sheet actuallyto be deflected. Consequently it is possible to deenergize the magneticroll just ahead of any imperfect sheet and to reenergize this rollimmediately after the trailing edge 13% of this sheet passes the roll.This very rapid and accurate action enables the mechanism to divertsingle imperfect sheets or any number of such sheets without divertingprime sheets. At the same time the mechanism virtually eliminates theneed for mechanically moving parts.

While I have shown and described only a single embodiment of theinvention, it is apparent that modifications may arise. Therefore, I donot wish to be limited to the disclosure set forth but only by the scopeof the appended claims.

I claim:

1. In a shear line for metal strip, which includes a. shear and primeand reject sheet pilers, a mechanism for classifying and assortingsheets comprising a deflector normally allowing sheets to pass to saidprime piler but operable to divert sheets to said reject piler, meansfor detecing imperfections in the strip ahead of said shear, meansoperatively connected to said detecting means and to said shear forrecording that a sheet cut by said shear contains an imperfection, meanssituated beyond said shear responsive to the passing of the leading edgeof a sheet thus recorded as imperfect for further recording that a sheetis imperfect, and time delay means operatively connected with saidfurther recording means for operating said deflector, whereby thereference point for operating said deflector is the leading edge of animperfect sheet. 7

2. In a shear line for metal strip, which includes a shear and prime andreject sheet pilers, a mechanism for classifying and assorting sheetscomprising a deflector normally allowing sheets to pass to said primepiler but operable to divert imperfect sheets to said reject piler,means for detecting imperfections in the strip ahead of said shear, astorage circuit operatively connected to said detecting means and saidshear and adapted to be cocked as said shear cuts from the strip a sheetcontaining an imperfection, means situated beyond said shear responsiveto passing of the leading edge of a sheet for triggering said storagecircuit, and time delay means responsive to triggering of said storagecircuit for operating said deflector whereby the reference point foroperating the latter is the leading edge of an imperfect sheet.

3. In a shear line for metal strip, which includes a shear and prime andreject sheet pilers, a mechanism for classifying and assorting sheetscomprising a deflector normally allowing sheets to pass to said primepiler but operable to divert imperfect sheets to said reject piler,means for detecting imperfections in the strip ahead of said shear,means driven at a rate proportional to the strip speed for recordingimperfections thus detected, a storage circuit operatively connectedwith said recording means to be cocked thereby when a recordedimperfection reaches said shear, a switch actuated by said shear whenthe latter cuts the strip and operatively connected with said storagecircuit for triggering the latter when cocked, a second storage circuitconnected with said first named storage circuit and adapted to be cockedby triggering thereof, means situated beyond said shear for triggeringsaid second storage circuit when cooked on passing of the leading edgeof the sheet, means driven at a rate proportional to the strip speed forrecording triggering of said second storage circuit, and meansoperatively connecting said second named recording means and saiddeflector for operating the latter.

4. In a shear line for metal strip, which includes a shear and prime andreject sheet pilers, a mechanism for classifying and assorting sheetscomprising a deflector normally allowing sheets to pass to said primepiler but operable to divert imperfect sheets to said reject piler,means for detecting imperfections in the strip ahead of said shear, amagnetizable recording track driven at a rate proportional to the stripspeed a magnetizing coil and a pickup cooperable with said recordingtrack and spaced proportionately to the spacing between said de- 14tecting means and said shear, an electronic control, a circuit in saidcontrol connecting said detecting means and said coil, a storage circuitin said control connected to said pickup and said shear and adapted tobe cocked by the former when an imperfection reaches said shear andtriggered by the latter when cutting a sheet containing theimperfection, a second storage circuit in said control adapted to becocked by triggering of said first storage circuit, means responsive topassing of a leading edge of a sheet for triggering said second storagecircuit when cocked, a second magnetizable recording track driven at arate proportional to the strip speed, a magnetizing coil and a pickupcooperable with said second recording track and spaced proportionatelyto the spacing between the triggering means for said second storagecircuit and said deflector, a circuit in said control connecting saidsecond storage circuit and said second named coil, and a circuit in saidcontrol connecting said second named pickup and said deflector.

5. In a shear line for metal strip, which includes a shear and prime andreject sheet pilers, a mechanism for classifying and assorting sheetscomprising a magnetic roll deflector normally energized and allowingsheets to pass to said prime piler but when de-energized divertingsheets to said reject piler, means for detecting imperfections in thestrip ahead of said shear, means driven at a rate proportional to thestrip speed for recording imperfections thus detected, a storage circuitoperatively connected with said recording means to be cocked therebywhen a recorded imperfection reaches said shear, a switch actuated bysaid shear when the latter cuts and operatively connected with saidstorage circuit for triggering the latter when cocked, a second storagecircuit connected with said first named storage circuit and adapted tobe cocked by triggering thereof, a photoelectric cell beyond said shearand connected to said second storage circuit for triggering the latterwhen cocked on darkening of the cell by the leading edge of a sheet,means driven at a rate proportional to the strip speed for recordingtriggering of said second storage circuit, and a circuit operativelyconnecting said second named recording means and said deflector forde-energizing the latter.

6. In a shear line for metal strip, which includes a shear and prime andreject sheet pliers, a mechanism for classifying and assorting sheetscomprising a magnetic roll deflector normally energized and allowingsheets to pass to said prime piler but when tie-energized divertingsheets to said reject piler, means for detecting imperfections in thestrip ahead of said shear, a magnetizable recording track driven at arate proportional to the strip speed, a magnetizing coil and a pickupcooperable with said track and spaced proportionately to the spacingbetween said detecting means and said shear, an electronic control, acircuit in said control connecting said detecting means and said coil, astorage circuit in said control connected to said pickup and adapted tobe cooked thereby when an imperfection in the strip reaches said shear,a switch actuated by said shear as it cuts the strip and connected tosaid storage circuit for triggering it, a second storage circuit in saidcontrol adapted to be cocked by triggering of said first storagecircuit, a photoelectric cell beyond said shear and connected to saidsecond storage circuit for triggering the latter when cocked ondarkening of the cell by the leading edge of a sheet, a secondmagnetizable recording track driven at a rate proportional to the stripspeed, a magnetizing coil and a pickup cooperable with said second trackand spaced proportionately to the spacing between said cell and saiddeflector, a circuit in said control connecting said second storagecircuit and said second named coil, and a circuit in said controlconnecting said second named pickup and said deflector fortie-energizing the latter.

7. In a shear line for metal strip, which includes a shear and prime andreject sheet pilers, a mechanism for classifying and asserting sheetscomprising a 'magnetic roll deflector, a grid controlled rectifierthrough which the magnets of said deflector normally are energized forallowing sheets to pass to said prime piler, but adapted when receivinga negative potential on its grids to de-energize the magnets fordiverting sheets to said reject piler, means for detecting imperfectionsin the strip ahead of said shear, a magnetizable recording track drivenat a rate proportional to the strip speed,

a magnetizing coil and a pickup cooperable with said track and spacedproportionately to the spacing between said detecting-means and saidshear, a circuit connecting Said detecting means and said coil, astorage circuit connected to said pickup and adapted to be cockedthereby whenan imperfection in the strip reaches said shear, a switchactuated by said shear as it cuts the strip and connected tosaid'storage circuit for triggering it when cocked, a second storagecircuit adapted'to be cocked by triggering of said first storagecircuit, means beyond said shear connected to said second storagecircuit for triggering it when cocked on passing of the leading edge ofa sheet, a second magnetizable recording track driven at a rateproportional to the strip speed, a magnetizing coil and a pickupcooperable with said second track and spaced proportionately to thespacing between the triggering means for said second storage circuit andsaid magnetic roll, a circuit connecting said second storage circuit andsaid second named coil, and a circuit connecting said second namedpickup and the grids of said rectifier for applying a negative potentialthereto as a magnetized spot on said second track passes said secondnamed pickup.

8. In a shear'line for metal strip, which includes a shear and'prirneand reject sheet pilers, a mechanism for classifying and assertingsheets comprising a magnetic roll deflector, a grid controlled rectifierthrough which the magnets of said deflector normally are energized forallowing sheets to pass to said prime piler, but adapted when receivinga negative potential on its grids to de-energize the magnets fordiverting sheets to said reject piler, means for detecting imperfectionsin the strip ahead of said shear, a magnetizable recording track drivenat a rate proportional to the strip speed, a magnetizing coil and apickup cooperable with said track and spaced proportionately to thespacing between'said detecting means and said shear, a circuitconnecting said detecting means and said coil, a storage circuitconnected to said pickup and adapted to be cocked thereby when animperfection in the strip reaches said shear, a switch actuated by saidshear as it cuts the strip and connected to said storage circuit fortriggering it when cocked, a second storage circuit adapted to be cockedby triggering of said first storage circuit, a photoelectric cell spacedbeyond said shear by more than one sheet length and a maximum of twosheet lengths and connected to said second storage circuit fortriggering the latter when cocked on darkening of the cell by theleading edge of a sheet, a second magnetizable recording track driven ata rate proportional to the strip speed, a magnetizing coil and a pickupcooperable with said second track and spaced proportionately to thespacing between said cell and said deflector, a circuit connecting saidsecond storage circuit and said second named coil, and a circuitconnecting said second named pickup and the grids of said rectifier forapplying a negative potential thereto as a magnetized spot on saidsecond track 7 passes said second named pickup.

9. In a shear line for metal strip, which includes a shear and prime andreject sheet pilers, a mechanism for classifying and asserting sheetscomprising a magnetic roll deflectona grid controlled rectifier throughwhich the magnets of said deflector normally are energized for al-'lowing'sheets to pass 'to said prime piler, but adapted when receiving anegative potential on its grids to deengize the magnets 'for divertingsheets to said reject piler, means for detecting imperfections, in thestrip ahead of.

15 said shear, a magrietizable recording track driven at a rateproportional to the strip speed, a magnetizing coil and a pickupcooperable with said track and spaced proportionately to the spacingbetween said detecting means and said shear, an amplifier circuit and apulse shaping circuit connecting said detecting means and said coil, astorage circuit connected to said pickup and adapted to be cockedthereby when an imperfection in the strip reaches said shear, a switchactuated by the shear, an amplifier circuit connecting said. switch andsaid storage circuit, actuation of said switch triggering said storagecircuit when cocked, a second storage circuit connected to said firststorage circuit and adapted to be cocked by triggering thereof, aphotoelectric cell spaced beyond said shear by more than one sheetlength and a maximum of two sheet lengths, a flip-flop circuitconnected'to' said cell and adapted to pass current one Way whenthe cellis exposed to light and another Way when the cell is darkened by apassing sheet, said flip-flop circuit being connected to said secondstorage circuit and triggering it when cocked on darkening of said cellby the leading edgecf a sheet, a second magnetizab le recording track'driven at a rate proportional to the strip speed, a magnetizing coiland a pickup cooperable with said second track and spaced proportionatlyto the spacing betweensaid cell and said deflector, a third storagecircuit and an oscillator connecting said second storage circuit andsaid second named coil, and an amplifier connecting said second namedpickup and the grids of said rectifier for applying a negative potentialthereto as a magnetized spot on said second track passes said secondnamed pickup. r

10. in a shear line for metal strip, which includes a shear and primeand reject sheet pilers, a mechanism for classifying and assortingsheets and marking defective sheets comprising a deflector normallyallowing sheets to pass to said prime piler but operable totdivertimperfect sheets to said reject piler, a pin hole detector ahead of saidshear, a marker between said detector and said shear, a magnetizablerecording track driven at a rate proportional to the strip speed, amagnetizing coil and a marker pickup and a circuit cocking pickupcooperable with said trackand spaced proportionately to the spacingbetween said detector and said marker and said shear respectively, anamplifier circuit and'a pulse shaping circuit connecting said detectorand saidcoil, an amplifier circuit connecting said marker pickup andsaid marker, a, storage circuit connected to said circuit cocking pickupand adapted to be cocked thereby when an imperfection noted by said detector reaches said shear, means connecting said shear with said storagecircuit for triggering the latter when cocked as the shear cuts thestrip, and time delay means for operating said deflector initi'ated'bytriggering of said storage circuit. V t i 11. A shear line asdefined inclaim 10in which the classifying and asserting mechanism includes meansfor transferring the reference point for operating said deflector totheleading edges of the sheets. 7

12. A shearrline as defined in claim 10 in which classifying andassortingrmechanisnr includes means for transferring the reference pointfor operating said deflector to the leading edges of the sheets and saidtime delay means includes a second magnetizable recording track, amagnetizing coil and a pickup cooperable therethe with andspacedproportionately to the spacing between said transferring means and 'saiddeflector, and circuits connecting said last named coil with saidtransferring means and said last named pickup with said deflector.

13. In a shear line for metal strip, which includes a shear and primeand reject sheet pilers, a mechanism for classifying and assertingsheets and marking defective sheets comprising a deflector normallyallowing sheets to pass .to said prime piler but operable to divertimperfect sheets to said reject piler, a pin hole detector ahead of saidshear, a marker between said detector and said shear, a magnetizablerecording track driven at a rate proportional to the strip speed, amagnetizing coil and a marker pickup and a circuit cocking pickupcooperable with said track and spaced proportionately to the spacingbetween said detector and said marker and said shear respectively, anamplifier circuit and a pulse shaping circuit connecting said detectorand said coil, an amplifier circuit connecting said marker pickup andsaid marker, a storage circuit connected to said circuit cocking pickupand adapted to be cocked thereby when an imperfection noted by saiddetector reaches said shear, a shear switch actuated by said shear as itcuts the strip and connected to said storage circuit for triggering itwhen cocked, a second magnetizable recording track driven at a rateproportional to the strip speed, a magnetizing coil and a pickupcooperable with said second track, transfer means connected to saidstorage circuit and said last named coil for energizing the latter onpassing of the leading edge of a defective sheet, and means connectingsaid last named pickup and said deflector.

14. A sheet classifying line comprising a shear, means for conveyinguncoiled continuous metal strip to said shear and sheets therefrom,prime and reject sheet pilers, a magnetic roll deflector between saidconveying means and said pilers normally having magnetic characteristicsto route sheets to said prime piler, means for detecting imperfectionsin the strip ahead of the shear, and means operatively connected to saiddetecting means and controlled by the leading edge of a sheet containingan imperfection for changing the magnetic characteristics of saiddeflector immediately ahead of the arrival of this sheet and by thetrailing edge of this sheet for resetting said deflector immediatelyafter departure thereof, said deflector routing sheets to said rejectpiler when its magnetic characteristics are thus changed.

15. A sheet classifying line comprising a shear, means for conveyinguncoiled continuous metal strip to said shear and sheets therefrom,prime and reject sheet pilers, a magnetic roll deflector between saidconveying means and said pilers normally having magnetic characteristicsto route sheets to said prime piler, means for detecting imperfectionsin the strip ahead of the shear, and a memory device and electroniccontrol connected with said detecting means and said shear for recordingthat an imperfection detected in the strip lies within a particularsheet cut by said shear said memory device and control also beingconnected with said deflector for changing its magnetic characteristicsimmediately ahead of the arrival of the leading edge of a sheetcontaining an imperfection to divert that sheet to said reject piler andfor resetting said deflector immediately after the departure of thetrailing edge of that sheet.

16. A sheet classifying line comprising a shear, means for conveyinguncoiled continuous metal strip to said shear and sheets therefrom,prime and reject sheet pilers, a magnetic roll deflector between saidconveying means and said pilers normally having magnetic characteristicsto route sheets to said prime piler, means for detecting imperfectionsin the strip ahead of the shear, means operatively connected to saiddetecting means and said shear for registering that a particular sheetcut by the shear contains an imperfection, photoelectric means situatedbetween said shear and said deflector and being operatively connected tosaid registering means, a recording track driven at a rate proportionalto said conveying means, means operatively connected to saidphotoelectric means and associated with said track for recording on saidtrack the movement past said photoelectric means of both the leading andtrailing edges of a sheet containg an imperfection, and a circuitactuated by said recording track and connected to said deflector forchanging its magnetic characteristics immediately ahead of the arrivalof the leading edge of a sheet containing an imperfection to divert thatsheet to said reject piler and for resetting said deflector immediatelyafter the departure of the trailing edge of that sheet.

17. A sheet classifying line comprising a shear, means for conveyinguncoiled continuous metal strip to said shear and sheets therefrom,prime and reject sheet pilers, a magnetic roll deflector between saidconveying means and said pilers normally having magnetic characteristicsto route sheets to said prime piler, means for detecting imperfectionsin the strip ahead of the shear, means operatively connected to saiddetecting means and said shear for registering that a particular sheetcut by the shear contains an imperfection, photoelectric means situatedbetween said shear and said deflector and being operatively connected tosaid registering means, a magnetic recording track driven at a rateproportional to said conveying means, a recording head cooperable withsaid track and connected to said photoelectric means for magnetizing anarc on said track commencing when the leading edge of a sheet containingan imperfection passtfi said photoelectric means and terminating whenthe trailing edge of that sheet passes, and a pickup cooperable withsaid track and spaced from said recording head a distance proportionalto the spacing between said photoelectric means and said deflector, saidpickup being con nected to said deflector to change its magneticcharacteristics when the beginning of a magnetized arc reaches thepickup to divert a sheet to said reject piler and to reset saiddeflector when the end of this are reaches the pickup.

18. In a shear line for metal strip, which includes a shear, prime andreject sheet pilers, and means for conveying sheets from said shear tosaid pilers, a mechanism for classifying and assorting sheets comprisinga deflector normally allow ng sheets to pass to said prime piler butoperable to divert sheets to said reject piler, means for detectingimperfections in the strip ahead of said shear, means operativelyconnected to said detecting means and said shear for initiallyestablishing the trailing edges of sheets which have imperfections asreference points for subsequently operating said deflector, means fortransferring the reference points for operating the deflector to theleading edges of the imperfect sheets and establishing the trailingedges of the imperfect sheets as reference points for resetting thedeflector, and time delay means operatively connected to said deflectorand to said transferring means for operating and resetting saiddeflector.

19. A method of classifying and assorting sheets comprising detectingimperfections in moving continuous strip, recording the imperfections,cutting said strip into individual sheets, identifying any sheetcontaining a recorded imperfection simultaneously with the cutting ofthis sheet from the strip, moving the sheets in a line away from thepoint of cutting, recording the passing of a given point in the line ofthe leading and trailing edges of sheets identifled as containingimperfections, diverting from the line at a subsequent point only thosesheets of which passing of the leading and trailing edges has beenrecorded, resetting the line after a sheet is diverted, and timing theresetting to occur when the trailing edges of sheets containingimperfections pass said subsequent point to enable a sheet immediatelyfollowing to continue in the line if free of imperfections.

20. A method of classifying and assorting sheets comprising detectingimperfections in moving continuous strip, recording the imperfections,cutting the strip into individual sheets, identifying any sheetcontaining a recorded imperfection simultaneously with the cutting ofthis sheet from the strip, moving the sheets in a line away from thepoint of cutting, recording the passing of a given point in the line ofthe leading edges of sheets identified as containing imperfections asreference points for deflecting such sheets, recording the passing ofthe same point of the trailing edges of sheets identified as containingimperfections as reference points for resetting, diverting from the lineat a subsequent point only those sheets of which passing of the leadingedge has been recorded, resetting the line after a sheet is diverted,and timing the resetting to occur when the trailing edges of sheets con

